Heresy! Smooth Wheel Covers- Myth Busted!!!

[Vekke]

If you are not able to test something accurately does not mean someone else cannot do better. O fcourse even these results there is variation. Last run 0,1kWh change came from temperature. The other variation came from start which reason is unknown to me at this point.
https://youtu.be/JhcDhwnwU0I

That 2nd run to east was off from start. Almost came to same result still.
5 times 16,4 and one time 16,3=98,3/6=16,38
4 times 14,1 and one time14,2=14,12
--> Average consumption in my test route 15,25kWh

What is the accuracy if you don`t take the temp changes into account?
I say its under 0,1 kWh accurate based on this set.

[JulianEdgar]

Originally Posted by Vekke

If you are not able to test something accurately does not mean someone else cannot do better. O fcourse even these results there is variation. Last run 0,1kWh change came from temperature. The other variation came from start which reason is unknown to me at this point.
https://youtu.be/JhcDhwnwU0I

That 2nd run to east was off from start. Almost came to same result still.
5 times 16,4 and one time 16,3=98,3/6=16,38
4 times 14,1 and one time14,2=14,12
--> Average consumption in my test route 15,25kWh

What is the accuracy if you don`t take the temp changes into account?
I say its under 0,1 kWh accurate based on this set.

1. If these are all records of your running average, taken one after the other on the one run, then only the figures at the end matter - otherwise, as had already been said, you're double counting. (That what you seem to have done in your calculation, but just confirming that for others who will see all the figures and think they're all for different runs.)

2. You cannot go from three significant figures (your readings) to four significant figures (your average). If you don't want to take my word for it, do some research - eg https://courses.lumenlearning.com/in...icant-figures/ ("The final answer in a multiplication or division problem should contain the same number of significant figures as the original number with the fewest significant figures.")

3. Therefore, your average is 16.4 one way, and 14.1 the other way. Therefore, on resolution alone, the smallest variation you can measure is 0.6 per cent one way and 0.7 per cent the other way. (If I were doing the testing, I'd in fact say that I couldn't expect to see any changes of less than 1 per cent, but I am very conservative.)

4. I think you'd need to do what I always do - do the runs standard (to set the baseline) and then make the aero change and then immediately redo the runs in modified form. Then, for best accuracy, remove the mods and redo the runs, ensuring the measured results match the first series of runs in that session. ie A / B / A.

6. And maybe stop listing the running averages that add nothing to the accuracy of anything?

[Vekke]

I count only the end results when calculating anything.

The other measuring points bring extra accuracy at least to me. If the results jump 0,2 units rapidly at the end of the run measuring there compared to previous ones there can be wind gusts, car heats or cools something. I shut down the ac and it has helped little to get even less variation.

On longer test runs if car is not performing any better than previous best the test can be aborted after 2 bad measurin point results. On the longer 100km tests I measure the consumption every 10km at the moment. But I wont go for longer tests unless there is new better performing parts from short tests to verified.

If the run would be more longer like +1 km it would bring more accuracy, but then again we are already at the limits of the accuracy of the dash 0,1 units so extra accuracy would be wasted in my eye. You would get better results if the last measuring point would be in more level ground, as then it would be more stable when taking the numbers. But there is no good level point in my route this road has twists and turns all the time. This leg has least cars going so it helps a lot.

On all mods tested if possible on and off runs are made which parts work better.

Yesterday was same time for testing but really windy. more headwind direction results changed 0,3 units on three runs and tailwind results were still same. Then averages were 17,5 and 13,5-->15,5

[JulianEdgar]

Originally Posted by Vekke

I count only the end results when calculating anything.

Good!

On longer test runs if car is not performing any better than previous best the test can be aborted after 2 bad measurin point results.

I don't understand - if it doesn't match what you want, you abort the run?!

To avoid just that bias I never analyse the results until all the data is in. Otherwise, much too easy to introduce your own bias.

If the run would be more longer like +1 km it would bring more accuracy, but then again we are already at the limits of the accuracy of the dash 0,1 units so extra accuracy would be wasted in my eye.

You're confusing 'resolution' and 'accuracy'.

[AeroMcAeroFace]

Originally Posted by JulianEdgar

If we could road test with accuracy down to 0.6 per cent drag variation then it would be fantastic - but based on the tech lit and my own testing, I don't think that's possible.

Considering wind tunnels aren't that close then I think it is impossible without compensating for all sorts of variables such as barometric pressures, instantaneous windspeeds, road surface temperatures, passenger weight changes, tyre temperatures, thrust generated by cooling fans etc. . I don't know what those factors add up to but I would guess at more than 0.6% on a day to day basis.

Maybe the changes would have less total effect if the tests were repeated immediately and many many times on many days with random A-B testing with a driver that doesn't know what they are testing.

[AeroMcAeroFace]

Originally Posted by Vekke

Then averages were 17,5 and 13,5-->15,5

the margin of error is nearly +/- 20%!

[Vekke]

I know percentage calculations are difficult I am not master either. 0,3 units from 17,5 average is 17,4 to 17,7 which means tolerance/error was +-0,8%.
Other direction 13,5kWh no error.

My front tire deflector change time is under 5 min per swap. On that time car wont cool down much and conditions dont change too much to have effect if they are steady to start with.

Again if you do longer tests you will get more variation from temperature and wind as its rarery steady and other cars. My todays 100km test was ruined by other cars at 30km point...

[JulianEdgar]

Originally Posted by Vekke

Again if you do longer tests you will get more variation from temperature and wind as its rarery steady and other cars. My todays 100km test was ruined by other cars at 30km point...

I am sorry, but that logic is very strange indeed.

[Phase]

https://core.ac.uk/download/pdf/211225703.pdf

seems like fully closed wheels increase the base pressure at the rear of the car. they also prevent air from coming out of the rims and feeding into the jetting vortex behind the wheel

[Phase]

https://odr.chalmers.se/bitstreams/8...dd89b/download

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